1. Field of the Invention
This invention relates to floor cleaning apparatus employing hot water sprayed against the floor surface to be cleaned, the water thereafter being retracted with a suction nozzle and brush arrangement to an extraction tank. In broad aspects, this invention relates to method and apparatus for heating a fluid.
2. Description of the Prior Art
The prior art has seen a wide variety of methods and apparatus for heating a fluid. It is also known in the prior art to use nozzles for discharging hot water against the surface of a carpet or the like to increase the efficacy of cleaning dirt and foreign material from the floor surface. Ordinarily, hot water in such embodiment is generated in a heating tank that includes an electrical heating element and is fed to the nozzles by pump. The extraction tank used in the prior art has a fan or other vacuum generating means in its upper surface and is connected to the vacuum nozzle on the floor unit by a flexible hose in the prior art. Such devices have a number of significant disadvantages including the difficulty in withdrawing sufficient amounts of moisture from the carpet to prevent a prolonged period of wetness and shrinkage. Also, complete dirt and soil extraction was not always effected because the water temperature was only in the range of about 130.degree. F. Typical of the closest prior art of which I am aware are the following U.S. Pat. Nos. 1,402,021; 1,402,873; 2,616,022; 3,133,182; 3,215,416; 3,439,374; 3,518,410 and 3,699,607; as well as British Pat. No. 1,430,989. For discussing the differences between those and the Applicant's invention, the references can be grouped. The references U.S. Pat. Nos. 3,133,182; 1,402,021; 1,402,873 and the British Pat. No. 1,430,989 all provide inadequate heating and in the cases where they use shorted secondaries, use two legged cores that lose efficiency of heating as in a three legged core. This loss of efficiency is due to the physical placement of the secondary on the core and the technique by which the secondary is shorted. In fact, the British Pat. No. 1,430,989 relies upon resistance type heating which is much too slow in the applications of this invention. In U.S. Pat. No. 3,215,416, the secondary coil is disposed about an iron core but is spaced longitudinally of the iron core from the primary coil, such that it is relatively inefficient and could not be employed advantageously in the applications of this invention. Similarly, U.S. Pat. No. 2,616,022 employs a shorted secondary in which the secondary coil is wrapped around an iron core remote from the primary coil and thus does not take advantage of the I.sup.2 R heating in the primary. The shorting bar of the secondary is remote from the coil and is exposed to the air for deliberate cooling and consequently suffers heat losses to the atmosphere. U.S. Pat. No. 3,518,410 is pertinent in employing a three legged core and the specific coil geometry but the secondary is shorted by a remote bar (similar to U.S. Pat. No. 2,616,022) and thus does not take advantage of having the shorted secondary completely within the collapsing field and contiguous the primary so as to take advantage of the I.sup.2 R loss type heating in both coils. Also, U.S. Pat. No. 3,518,410 has a higher resistance, thus limiting the current flowing in the secondary, as contrasted with a shorted secondary. Consequently, its apparatus does not produce as much I.sup.2 R heating and, therefore, is less efficient. U.S. Pat. No. 3,699,607 employs a cylindrical brush in conjunction with a water vacuum but does not provide a totally satisfactory solution since the water was heated so slowly that it was not hot enough to be effective as needed. Particularly, the prior art has not supplied fluid heating apparatus or floor cleaning apparatus that operated so fast that it obviated the necessity for pre-heating the fluid such as water.